When treating certain medical conditions, it is sometimes desirable to expand a frame or other radially expandable member in an orifice or conduit of a patient's body. For example, expandable tubes called stents are commonly inserted into a natural conduit of a patient's body and expanded inside the conduit to hold the conduit in an open position. Such expandable stents can be used to expand, widen, or otherwise provide structural support to various conduits of the human body, including, for example, arteries, veins, bile ducts, the esophagus, and the colon. In other treatment procedures, prosthetic heart valves that include a frame member are implanted into the body at a treatment site (e.g., a heart valve annulus). These prosthetic heart valves can be positioned in the heart valve annulus by expanding the frame member to roughly the size of the valve annulus.
The expansion of such frames in the body can be performed using an expansion device, such as a balloon. For example, a method can involve positioning a frame on a balloon of a balloon catheter, maneuvering the balloon and frame to the treatment site, and inflating the balloon with a fluid to expand the frame to the desired size. Many orifices or conduits in the body, such as the native aortic valve annulus, have non-cylindrical shapes. Unfortunately, current expansion devices and methods do not provide a convenient and effective way to expand a frame or other expandable member so that it conforms to a non-cylindrical orifice or conduit.